Triode ionic pump



Jan- 11, 1966 W. J. KEARNS ETAL 3,228,590

TRIODE INIG PUMP Filed Jan. 2, 1964 TH El R ATTORNEY.

United States Patent O 3,228,590 TRIODE IONIC PUMP William Joseph Kearns, Peter J. Clarke, and Thomas A. Vanderslice, ali of Scotia, N.Y., assignors to General Electric Company, a corporation of New York Filed Jan. 2, 1964, Ser. No. 335,310 9 Claims. (Cl. 230-69) This invention relates to triode ionic pumps, and more particularly, to a triode ionic pump configuration having a single unitary electrode assembly or structural unit incorporated therewith to provide an improved, high efficiency pump on the order of 25 liters per second capacity.

As a result of increasing use and wider application of triode ionic vacuum pumps, there has been indicated a need for triode ionic pumps of increased efiiciency at relatively low capacities on the order of about 25 liters per second. It has been furthermore indicated that these pumps are required to be of a simple design which not only facilitates their removal and replacement but also the removal and replacement of their internal .parts and assemblies. -At the same time their simplified design should contribute to their high efficiency and to moderate costs in their manufacture.

Accordingly, it is an object of this invention to provide an improved triode ionic pump.

It is another object of this invention to provide an improved unitary electrode assembly in conjunction with a low capacity ionic pump.

It is a further object of this invention to provide an improved triode ionic pump of simplified and interchangeable design.

It is another object to provide an improved triode ionic pump with improved manufacturing, assembling and operating features.

Briefly described, this invention includes in one preferred form, a pump housing having a lower rectangular cross-section portion, and an upper circular transition'section which incorporates within the rectangular section a unitary electrode structure assembly. The mentioned electrode :assembly cooperates with the rectangular portion of the housing which functions as a collector electrode, to provide an improved efficiency 25 liter per second triode ionic pump.

This invention will be better understood when taken in connection with the following description and the drawings in which,

FIG. 1 is an end-elevational view of one preferred embodiment of this invention, and

FIG. 2 is a side-elevational view of the invention as illustrated in FIG. 1.

Referring now to lFIG. 1, there is illustrated a pump assembly 10 including a chamber or housing unit 11 fitted with a circular opening defining flange 12 for joining to an apparatus to be evacuated. Housing unit 11 includes a lower narrow rectangular volume section 13 and an upper transitional circular volume section 14 extending well below fiange 12 to have substantial depth. A unitary electrode structure is included in housing 11 within the rectangular section 13 thereof. While the housing unit 11 may include various modifications of material and structure, in the improved version of this invention, housing 11 is manufactured of stainless steel, for example, and by a drawing or forming process which precludes any need of additional welded seams which would provide potential sources of gas leaks. In addition, housing 11 is manufactured so that the circular section 14, which may also be a smoothly flaring or tapered portion between section 13 and ilange 12, is a transitional section providing additional or improved gas conductance Vbetween the apparatus to be evacuated and the unitary electrode structure 15.

3,228,590 Patented Jan. 11, 1966 ICC In order to provide increased gas conductance the transitional section 14 should be of substantial depth or height, i.e., the distance between flange 12 and section 13 should be about the proportion as indicated in FIG. 1 so that abrupt changes are avoided. Furthermore, the substantially increased cross-section of section 14 permits working `freedom therein for assembly, disassembly and han dling purposes.

Electrode structure 15 in one preferred embodiment of this invention is the unitary structure disclosed in copending application Serial No. 316,694 filed October 16, 1963, and assigned to the same assignee as the present invention. More particularly, electrode structure 15 includes a central planar and rectangular anode structure 16 and a pair of planar and rectangular outer sputter cathode electrodes 17 and 18 positioned one on each side of grid 16 and coplanar therewith. The use of the specifically described unitary electrode structure permits ready interc'hangeability and standardization. For example, these same unit structures are available for a series of .pumps of different capacities, and combining or adding individual unit structures provide pumps of increasing capacities. It is thus an important feature that this electrode structure be employed as described. The unitary feature of this electrode assembly is further described with respect to FIG. 2.

Referring now to FIG. 2, anode electrode 16 is illustrated as being of an open, foraminate, or grid-like structure of substantial electron transparency. In one preferred form of this invention, grid 16 comprises a series of interiitting titanium strips of between about 0.002 to 0.015 inch thickness and :about 1/2 inch in width forming individual square openings of 1/2 inch square. The grid structure may also have individual openings of circular, hexagonaland other cross sections, these openings being in a range of about 1A; to 1/2 inch across the opening. The number, and also the size, of these individual openings may be varied over a wide range without detracting from the effectiveness of this invention. Anode electrode 16 is illustrated as 'being suitably joined to a supporting stainless steel bar 19 by joining means 20 and 20 which are also employed to positionsputter cathode electrodes 17 and 18 on each side of grid electrode 16, and to suitably electrically insulate sputter cathode electrodes 17 and 18 from grid :anode 16.

Joining means 20 and 20 with the mentioned positioning and insulating features are similar, so that a description of one suffices for the other. For example, assembly 2t) includes a central cylindrical electrically insulating member 21 positioned with its base in contact with the side of support bar 19 which is opposite from grid anode 16. While various insulating materials may be employed for cylinder 21 it is preferred that the material be a good insulator material over a wide temperature range, have good structural integrity, and be substantially gas free or free lfrom evolving substantial amounts of gas. Suitable exemplary materials are alumina, forsterite or steatite and other ceramic and stone-like materials. Ceramic cylinder 21 is maintained in tight engagement with support bar 19 by attaching means, for example, a stainless steel machine screw 22 which projects through uppermost strip 23 of grid 16, through an :appropriate aperture in support 19, and threadedly engages the interior of the ceramic cylinder 21. For additional stiffness in the supporting structure, stri-p 23 may be a thicker or double strip. Thereafter a cup-shaped sputter shield 24, for example of stainless steel, is positioned concentrically with and over cylinder 21 so that the side walls of cup shield 24 depend downwardly :about cylinder 21 to protect cylinder 21 from the deposits of sputtered metal. If desirable, additional sputter shield cup members may also be employed, for example at the bottom of cylinder 21 and 3 lapping the downwardly depending walls of sputter shield 24.

Sputter cathodes 17 and 18 are also supported from the insulator cylinders 21, only two of which are required to support all elect-rodes in their assembled and operative relationship. One supporting means utilized to provide proper between spacing and support of sputter electrodes 17 and 18 is illustrated in FIGS. 1 and 2 as U-shaped members and 25. As best illustrated in FIG. 1y U-shaped member 25 is of a metal, preferably stainless steel, and of suiiicient thickness `to provide structural integrity, i.e.J about 1/16 of an inch thick for one preferred embodiment of this invention. The U-shaped member 25 is positioned so that the inside base of the U-shape rests upon sputter shield 24 and ceramic cylinder 21, and the arms 26 and 27 of U-shaped member 25 depend downwardly at the front and rear of grid electrode 16. A suitable aperture is provided in the base of U-shaped member 25 and in sputter shield 24 so that attaching means in the form of, for example, a stainless steel machine screw 28 may project through U-shaped member 25, sputter shield 24 and threadedly engage ceramic insulator 21.

As illustrated in FIG. 2, each of the sputter cathodes 17 and 18 are similar so that a description of one suiiices for the other. For example, sputter cathode 17 comprises a frame 29 of a suitable metal such as `stainless steel supporting a grid element or structure 30. The structural configuration of element 30 is the same as that of grid anode 16 but with individual grid openings of a much smaller dimension. For example, grid element 38 as illustrated in FIG. 2 comprises a square grid formation of thin titanium strips of a thickness of about 0.002 to 0.015 inch and about 1/s inch in width. The particular cross-sectional cell configuration may `also take the form of various polygons, circles, etcetera, being, in one preferred embodiment of this invention, of a honeycomb hexagonal configuration of about lAG to l; inch across the iiats and suitably joined to `frame member 29 by welding. Frame member 29 also includes upstanding lug or ear portions 31 which lie underneath the respective depending arms 26 and 26 of U-shaped members 25 and 25'. For example, the upstanding portion 31 as illustrated in FIGS. 1 and 2 is positioned to lie adjacent to and under depending arm members 26 and 26. Thereafter, frame 29 is secured to the U-shaped members, for example by means of stainless steel screw 32, which passes through a depending arm and threadedly engages an upstanding ear.

Referring again to FIG. 1, in order to provide additional stiffness to the unitary electrode structure 15 and to maintain the lowermost extremities of the sputter cathodes 17 and 18 in predetermined spaced-relationship, suitable spacer or bracing means, for example stainless steel strips 33, are welded across frame members 29 of sputter cathodes 17 and 18. As illustrated in FIG. 2, one strip 33 is welded to frame members 29 on each side or end thereof.

To support the electrode structure 15 within housing 11, the supporting means as illustrated in FIG. 2 is ernployed. In FIG. 2, in the uppermost portion of the rectangular volume section 13 of housing 11, there is positioned suitable `attaching or supporting means in the form of for example an angle brace 34 which is welded to housing 11 on the narrow end wall of rectangular section 13. Similarly, a further angle brace 34' is attached to the 'housing 11 at the opposite narrow end wall of rectangular section 13. Support bar 19 of the electrode 15 assembly then spans the two support elements 34 and 34' and rests thereupon. Engaging means in the form of for example stainless steel screws 35 and 35' then project through support bar 19 to threadedly engage angle brace members 34 and 34. The described supporting means provides removal of the entire electrode assembly 15 from the pump or housing 11 merely by removing the two screw attaching means 35 and 3S.

Further advantages of the structural features of this invention relate to the fact that the change in dimension or configuration change between rectangula-r section 13 and circular section 14 also provides a shoulder or base upon which a suitable magnet structure may be positioned. In FIG. l a general magnet structure 36 is illustrated with its pole faces adjacent and parallel to the side walls of section 13. In this respect, the arrangement for relative positioning of the elec-trode assembly and the magnet is such that portions of the electrode structure 15 such as the ceramic insulator support means 21 are maintained out of the stronger tiel-d portion of the magnet structure 36.

In order to provide a suitable electrical connection to the electrode structure 15, an insulating and vacuum sealing connector structure 39, as lshown in FIG. 1, is attached to the circular portion of casing 11. Connector structure 39 includes a central stud element 40 containing apertures or bores 41 and 42 at opposite ends thereof which are adapted to retain electrical lead elements for power input to the pump. Stud element 4t) is surrounded in lateral spaced relationship by an insulator cylinder or sleeve 43 which is joined to the stud element 4t) at the outer head end 44. An electrically conductive metal cap 45 then fits over the end of sleeve 43 and underlies and joins head 44. At the other end of connector 39, a metal sleeve element 46 peripherally engages sleeve 43 at one end and is secured to a welding adapter 47 at the other end. Adapter 47 is welded to housing 11. From the inside of housing 11 a suitable electrical conductor, in the form of for example stainless steel lead wire 48, connects from the connector 39 to electrode structure 15. One type of connection includes a spring loop 49 which is forced into aperture 42 of stud element 40. Stainless steel wire 48 may be attached to the cathode structure, for example by screw means 50 threadedly engaging one of the U-shaped members 25. By this electrical connection means the sputtered cathode electrodes 17 `and 18 of the electrode structure 15 are connected to a source of high negative potential while the anode 16 and housing 11 are, as illustrated in FIG. 1, operative at ground potential.

By means of the illustrated described electrode structure in combination with the improved gas iiow conductance of the housing assembly, and the operation of this assembly with the sputtered cathodes at high negative potential and the anode and housing at ground potential, a new `and improved low capacity triode ionic vacuum pump is provided. A'll necessary parts have been reduced to a minimum while the important parts such as the insulators are not only reduced to the minimum but are placed in an optimum position within the apparatus. Only two insulators are employed `at the top or uppermost portion of the electrode assembly so that the electrode assembly 15 depends into the rectangular section 13 of casing 11. In conjunction with this pump as illustrated and described the sealing means 52 for flange 12 takes the form of those sealing means as illustrated and described in co-pending application Serial No. 295,120 Kearns.

Briefly described in this operation of this invention, those electrons which are in the defined space between anode 16 and sputter cathodes 17 and 18 are -attracted toward anode 16 by the positive electric field provided by having anode 16 at ground or positive potential with respect to sputter cathodes 17 and 18. The magnetic field generated between pole faces 37 and 38 of magnet 36 forces these electrons to move in long spiral patterns, greatly enhancing the number of collisions between these electrons and any gas molecules in the pump housing. Each ionizing collision between an electron and a gas molecule produces an ion which is attracted toward sputter cathodes 17 and 18 which are maintained at a high negative potential. Those ions which collide with the sputter cathode grid, collide at an oblique angle, which is most effective in sputtering metal from the cathodes` This sputtered metal is then sprayed on collector electrode surfaces of the housing 11 which faces the cathode. In one operative form of this invention the collector electrode surfaces are the larger inside surfaces or walls 51 of rectangular section 13, which face the electrodes in coplanar relationship. This spraying buries gas ions which have been driven toward the collector electrode surface and which arrive there with low velocity, and also provides clean active gettering material surface to additionally take up gases. Because the sputter cathode members 17 and 18 are of a high transparency gridded form, ions moving from the anode region may pass through the sputter lcathode structure without striking Iany part thereof. In this occurrence, the ions lose velocity after passing through sputter cathodes 17 and 18, because of the retarding eld between the adjacent collector electrode surface 51 and its adjacent sputter cathode, and arrive there with low or essentially zero velocity to be buried as mentioned above. Those which do not quite reach the collector electrode surfaces are then accelerated in a reverse direction, back toward the adjacent sputter cathode, where they can collide with oblique incidence, spraying metal toward anode 16. It is possible for an ion to make several excursions before being collected. It is the combination of oblique sputtering at the sputter cathode and the low velocity of arriving ions at the collector electrode surfaces which accounts for high pumping `speed of this triode pumping unit for rare gases. It also accounts for the low rate of re-emission of gases from the collector electrode, thus eliminating the argon instability, i.e., pressure fluctuation due to release lof previously pumped gases, so common in diode ionic pumps.

While this invention has been described with reference to particular and exemplary embodiments thereof, it is to be understood that numerous changes can be made by those skilled in the art without actually departing from the invention as disclosed, and it is intended that the appended claims include all such equivalent variations as come within the tr-ue spirit and scope of the foregoing disclosure.

What we claim as new and desire to secure by Letters Patent of the United States is:

ll. A relatively low pumping capacity triode ionic vacuum pump comprising in combination (a) a housing unit defining a pump chamber having a llanged opening and spaced planar sidewalls,

(b) a single unitary electrode assembly in said housing unit,

(c) said electrode assembly including support means spanning said chamber adjacent said flange opening and releasably secured to said housing,

(d) an electrical insulator on said support means on the ilange opening side thereof,

(e) a grid anode having predetermined opening sizes and attached by means of said insulator to said support means to extend into said chamber,

(f) a sputter shield member about said insulator,

(g) cathode support means attached to said insulator,

(h) a pair of cathode grids attached to said cathode support and positioned one `on each side of said anode grid,

(i) said cathode grids having openings of a predetermined size which is less than that of said grid anode,

(j) spacer means attached to said cathodes to maintain them in spaced relationship,

(k) `said cathode grids positioned in said housing to be in coplanar relationship with the said planar walls of said housing,

(l) and electrical connection means to connect said unitary electrode assembly and said housing to a `source of power to establish a glow discharge between said electrodes so that cathode material is sputtered and deposited on said housing for gas entrapment.

2. r1`he invention as recited in claim 1 wherein a pair only of said insulators are provided.

3. The invention as recited in claim 1 wherein said support means is releasably secured to said housing at two points only.

4l. The invention as recited in claim 1 wherein said housing unit is defined by a lower rectangular volume section to contain said electrode assembly and an upper cylindrical volume section of substantial depth.

5. The invention as recited in claim 4 wherein said Volumes are defined by a one-piece seamless casing.

6. The invention as recited in claim 1 wherein said electrical connection means includes an insulating connector in the side wall `of said housing, said connector comprising in combination (a) an insulating ceramic sleeve,

(b) an electrical conducting stud positioned concentrically with and spaced within said sleeve with one end extending a substantial distance from one end of said sleeve and into said housing,

(c) said stud having axial openings in each end there- (d) cap means on the outer end of said sleeve and attached to sa-id stud to aflix said stud to said sleeve,

(e) a metal sleeve bonded to the inner end of said sleeve and extending axially therefrom and surrounding said stud,

(f) means joining said metal sleeve to said housing so that said stud projects therewithin, and

(g) each said stud openings -acting as bayonet electrical connections to connect a source of electrical power to said electrodes.

7. A relatively low pumping capacity triode ionic vacuum pump comprising in combination (a) a housing unit,

(b) said unit having an interconnecting narrow rectangular volume section and a cylindrical volume flange section,

(c) a unitary electrode assembly releasably secured in said rectangular section,

(d) said lunitary electrode assembly including a supporting bar member extending across the narrow end walls of said rectangular section,

(e) means for releasably securing said bar member to each narrow end of said rectangular section,

(f) a pair of electrical insulators spaced along one side of said bar,

(-g) a planar grid anode attached to said insulators from the opposite side of said bar and extending into said rectangular section in parallel relationship with the larger side walls thereof,

(h) a cup-shaped sputter shield coaxially positioned on each said insulator,

(i) cathode support means attached to said sputter shield on said insulators,

(j) a pair of planar grid cathode electrodes attached to said support means in coplanar relationship with and one on each side of said grid anode and spaced therefrom,

(k) said grid anode and cathodes having openings therethrough of substantial depth and :of predetermined size with the opening size of said cathodes being less than that of said grid anode,

(l) spacer means positioned oppositely from said cathode support means and attaching sai-d cathodes together in spaced relationship and (in) electrical connection means on one of said cathodes to provide an electrical connection from a source of high potential to said cathodes so that said cathodes are operative at .high potential and said anode at low potential to establish a glow discharge therebetween and cause sputtering of said cathode material on said housing for gas entrapment thereby.

8. The invention as recited in claim 7 wherein said electrical connection means includes an insulating connector in the side wall of said housing, said connector comprising in combination (a) an insulating ceramic sleeve,

(b) `an electrical stud positioned concentrically with and sp-aced within said sleeve with ione end thereof extending a substantial distance from the inner end of said sleeve,

(c) said stud having coaxial openings in each end thereof,

(d) cap means on the outer end of said sleeve and attached to said stud to -aftix said stud to said sleeve,

(e) a metal sleeve bonded to the inner end of said sleeve and extending axially therefrom7 (f) means joining said metal sleeve to said housing so that said stud projects therewithin,

(g) said stud openings acting as bayonet electrical connection to connect a source of electrical power to said electrodes.

9. A triode ionic vacuum pump comprising in combination (a) a housing unit,

(b) said housing unit having an interconnecting narrow rectangular volume section and ya cylindrical volume ange section,

(c) said rectangular and cylindrical sections dening a shoulder section adapted to support a magnet structure,

(d) a unitary electr-ode assembly releasably secured in said rectangular section,

(e) said unitary electrode assembly including an intermediate planar Igrid anode and a planar sputter grid cathode on each side thereof,

(f) and means providing an electrical connection from said sputter grid cathodes to a source of high potential and from said anode and said housing to a low potential to establish glow discharge therebetween to cause sputtering of said sputter cathode material on the walls of said housing for gas entrapment thereby.

References Cited by the Examiner UNITED STATES PATENTS 3,018,944 1/1962 Zaphiropoulos a 230--69 3,080,164 3/1963 Vanderslice 230-69 3,115,297 12/1963 Lloyd et al. 230-69 FOREIGN PATENTS 949,219 2/1964 Great Britain.

OTHER REFERENCES German Printed Application No. 1,075,272, 2-1960.

lviARls'` NEWMAN, Primary Examinez'.

WARREN E. COLEMAN, Examiner. 

1. A RELATIVELY LOW PUMPING CAPACITY TRIODE IONIC VACUUM PUMP COMPRISING IN COMBINATION (A) A HOUSING UNIT DEFINING A PUMP CHAMBER HAVING A FLANGED OPENING AND SPACED PLANAR SIDEWALLS, (B) A SINGLE UNITARY ELECTRODE ASSEMBLY IN SAID HOUSING UNIT, (C) SAID ELECTRODE ASSEMBLY INCLUDING SUPPORT MEANS SPANNING SAID CHAMBER ADJACENT SAID FLANGE OPENING AND RELEASABLY SECURED TO SAID HOUSING, (D) AN ELECTRICAL INSULATOR ON SAID SUPPORT MEANS ON THE FLANGE OPENING SIDE THEREOF, (E) A GRID ANODE HAVING PREDETERMINED OPENING SIZES AND ATTACHED BY MEANS OF SAID INSULATOR TO SAID SUPPORT MEANS TO EXTEND INTO SAID CHAMBER, (F) A SPUTTER SHIELD MEMBER ABOUT SAID INSULATOR, (G) CATHODE SUPPORT MEANS ATTACHED TO SAID INSULATOR, (H) A PAIR OF CATHODE GRIDS ATTACHED TO SAID CATHODE SUPPORT AND POSITIONED ONE OF EACH SIDE OF SAID ANODE GRID, (I) SAID CATHODE GRIDS HAVING OPENINGS OF A PREDETERMINED SIZE WHICH IS LESS THAN THAT OF SAID GRID ANODE, (J) SPACER MEANS ATTACHED TO SAID CATHODES TO MAINTAIN THEM IN SPACED RELATIONSHIP, (K) SAID CATHODE GRIDS POSITIONED IN SAID HOUSING TO BE IN COPLANAR RELATIONSHIP WITH THE SAID PLANAR WALLS OF SAID HOUSING, (L) AND ELECTRICAL CONNECTION MEANS TO CONNECT SAID UNITARY ELECTRODE ASSEMBLY AND SAID HOUSING TO A SOURCE OF POWER TO ESTABLISH A GLOW DISCHARGE BETWEEN SAID ELECTRODE SO THAT CATHODE MATERIAL IS SPUTTERED AND DEPOSITED ON SAID HOUSING FOR GAS ENTRAPMENT. 